A microelectronic package comprises a microelectronic die electrically interconnected with a carrier substrate, and one or more other components, such as electrical interconnects, an integrated heat spreader, a heat sink, among others. An example of a microelectronic package is an integrated circuit microprocessor. A microelectronic die comprises a plurality of interconnected microcircuits within a single carrier to perform electronic circuit functions. A microelectronic device is defined as a microelectronic die with microcircuits electrically interconnected with electrically conductive pathways on the surface of or within a carrier substrate. Electrical communication between the microcircuits and external components is provided by electrically interconnected conductive pathways of the carrier substrate with electrically conductive pathways of a system substrate. An example of a system substrate is a printed circuit board (PCB), which, in some applications, is referred to as a motherboard.
Microelectronic dice generate heat as a result of the electrical activity of the microcircuits. As microelectronic dice are designed to operate at ever-increasing demands, heat generation also increases. In order to minimize the damaging effects of heat, passive and active thermal management devices are used. Such thermal management devices include heat sinks, heat spreaders, and fans, among many others. There are limitations in the use of each type of device, and in many cases, the thermal management device is specifically designed for a particular microelectronic die and package design and intended operation.
Heat sinks are one type of passive thermal management device. The principle behind a heat sink is a transfer of heat from the surface of the microelectronic die to a large thermal mass, which itself incorporates a large surface area for convective transfer the heat to the surrounding environment. Effective heat sinks tend to be very large and have sophisticated design with regards to fins and or pin heat releasing surfaces.
Integrated heat spreaders (IHS) are passive thermal conducting lids or caps placed in intimate thermal contact with the backside or inactiveside of the microelectronic die. Integrated heat spreaders also have sides that extend to seal against the carrier substrate, containing and protecting the microelectronic die and the electrical interconnects from the environment. Integrated heat spreaders also spread the thermal energy from localized areas on the microelectronic die surface to other areas of the die surface not only to mitigate local hot spots, but in some cases the microcircuits operate more efficiently if the die is a uniform temperature. The integrated heat spreader also provides an enlarged flat surface into which a heat sink may be attached.
Non-uniform power distribution within the microelectronic die results in local areas of high heat flux (hot spots) that must be mitigated. The root cause of the localized high heat flux is a result of the circuit layout having a highly non-uniform power distribution across the die.
The thermal management device must be able to maintain these hot spots at or below a specified temperature. This is very difficult when the local heat can be 10-times the microelectronic die average. Current devices are overwhelmed and limited in their ability to mitigate these local high heat flux sources. The thermal resistance between the heat sink and/or heat spreader is not low enough to adequately provide the necessary thermal mitigation in a reasonably sized system. Current devices cannot address the fundamental problem of power non-uniformity within the microelectronic die.
Apparatus and methods are needed to mitigate the effects of non-uniform power distribution and for providing the required heat flux distribution across the microelectronic die. They must provide for exceptionally small-scale integration, not interfere with the electrical interface of other components within the microelectronic package, and inexpensive to manufacture.